The function of the pulvinar nucleus is largely unexplored, although it is thought to play a key role in visual attention and visual motion perception. Recently the pulvinar nucleus has gained attention because it has been found to be significantly smaller in schizophrenic brains when compared to controls, and studies of patients with restricted lesions of the pulvinar nucleus exhibit some of the same visual deficits experienced by schizophrenic patients. Therefore further study of the pulvinar nucleus could shed light on brain circuits affected by schizophrenia. The proposed experiments focus on the physiological response properties and synaptic organization of the pulvinar nucleus and its projections to the striatum and amygdala, with the goal of elucidating how these circuits are modulated by the neurotransmitter gamma amino butyric acid (GABA). Anatomical experiments will determine whether separate cell types project to the striatum and amygdala using tract tracing and confocal microscopy. Immunocytochemistry and electron microscopy will be used to compare the GABAergic innervation of pulvinar neurons that project to the striatum or amygdala, and physiological experiments will compare the responses of these two cell types to moving visual stimuli in the presence or absence of the GABA receptor antagonist bicuculline. The proposed studies will use the tree shrew (Tupaia belangeri), which is considered to represent a prototype of early prosimian primates. Therefore our results should be easily related to primate brain organization, and could shed light on human disorders, such as schizophrenia. PUBLIC HEALTH RELEVANCE: Studies of patients with restricted pulvinar lesions have revealed a wide array of visual deficits, including the diminished ability to filter distracting signals, difficulty in binding image features, or difficulty in recognizing facial expressions. Because schizophrenic patients exhibit similar deficits, and the pulvinar nucleus of schizophrenic patients has been shown to be smaller than that of control subjects, our proposed studies could shed light on potential pulvinar pathways involved in symptoms of this disease.